A small bulb containing a conducting gas, an arc being formed between a metal ring and a tiny zirconium electrode near the center of the ring. The heated zirconium emits light, and constitutes a convenient laboratory point source.

The Foucault test is performed by moving a knife edge laterally into the image of a small point source. The eye, or a...

The position and shape of the image of a point source, as predicted by geometric optics alone. The geometric image is to be...

A test for spherical aberration, coma or astigmatism in which incident rays from a point source are isolated by small holes...

A point source of light used for the test and evaluation of image quality. May be a backlit pinhole in an otherwise opaque...

A cylindrical lens that may be rotated to distort a bundle of light originating at a point source, to form a line image.

The distribution of energy about the image of a point source in the focal plane of an optical system.

The figure seen through or imaged by an optical system. It may contain structures, natural or artificial, or it may be the...

Seidel aberrations refer to a set of monochromatic aberrations in optical systems, named after the German mathematician and...

A measure of image quality produced by an optical system. May be specified in terms of cycles per millimeter, referencing a...

A series of permanent holograms in dichromated gelatin formed by opening total page-composer apertures and setting a point...

The point spread function (PSF) is a fundamental concept in imaging that describes the response of an imaging system to a...

A narrow cone of light rays that diverge from a point source or converge to an image point.

An optical device that produces a line image lying along the axis from a point source of light; therefore, it has no...

SI unit of luminous intensity. It is defined as one sixtieth the normal intensity of one square centimeter of a blackbody at...

A method of demonstration or examination using a point source illumination without the use of any projection lens between...

The image of a point source that appears as a circle of finite diameter because of defocusing or the aberrations inherent in...

A lamp, usually incandescent, that has a very compact filament, permitting a greater concentration of emitted light, aided...

An imaging technique in which an object moving through an interference field formed in space scatters light and is spatially...

A method of producing magnified images by x-rays. The specimen is placed close to a point source of x-rays; the...

A bright spot or point, due to Fresnel diffraction, that appears at the center of the shadow of a circular object in light...

The law stating that the illuminance (or irradiance) from a point source varies as the inverse square of the distance...

Celestial point sources that emit specific wavelengths of radiation that appear on spectral charts as narrow lines. The term...

A lumen is a unit of measurement used to quantify the amount of luminous flux, which is the perceived power of light. In...

Totally coherent radiation is produced by a purely monochromatic point source. In the real world the energy will have a...

Condition in which a perpendicular surface can be discovered for every ray in a group. This condition is commonly observed...

Two plane mirrors that are not wholly located in the same plane. When light from a point source or slit reflects from the...

The visual examination by a trained observer of the image of a point source. Any coloring or departure from the Airy disc...

1. With respect to angular subtense, a source of light, such as a star, that is very small. In a lab, a point source may be...

A radiation source that, unlike the point source, can be resolved by the naked eye into a geometrical image.